There are many wintering bird species that are irruptive or alter their wintering location from year to year. The reasons for this are unknown, but could be linked to large scale climatic events that alter available resources. Additionally, it is important to understand the full range of a speciesâ winter distribution, and migration corridors so that the full range of areas used under various climatic conditions can be targeted for conservation. This visualization examines the distribution and migration patterns of 14 bird species during El Nino, La Nina, or neutral years.
ENSO El Nino southern oscillation
BASP Baird’s Sparrow, BRSP Brewer’s Sparrow, BTSP Black-throated Sparrow, CASP Cassin’s Sparrow, CCLO Chestnut-collared Longspur, GRSP Grasshopper Sparrow, LALO Lapland Longspur, LCSP LeConte’s Sparrow, MCLO McCown’s Longspur, SAGS Sagebrush Sparrow, SAVS Savannah Sparrow, SEWR Sedge Wren, SMLO Smith’s Longspur, VESP Vesper Sparrow
CCLO change or expand their winter range in El Nino years, SMLO change or expand their winter range in El Nino and La Nina years, and LCSP and SEWR expand their winter range in La Nina years. The other species visualized do not have any obvious winter range shifts.
Brewer’s sparrows seem to move north earlier in El Nino years, and seem to have a more concentrated winter distribution in La Nina years compared to neutral years.
Black-throated sparrows show fairly consistent wintering distributions and migratory patterns regardless of climatic year type.
Cassin’s sparrows are unique in that they migrate east-west. This east west migration with some northward movement is visualized below. It appears like migratory patterns may be more widely distributed during La Nina years.
The summer distribution of chestnut-collared longspurs seems more diffuse in La Nina years, while the winter distribution seems more concentrated in La Nina years, and more spread out in El Nino years. Additionally, in El Nino years chestnut-collared longspurs seem to migrate earlier and both arrive on their non-breeding range earlier, and leave their non-breeding range earlier.
Grasshopper sparrows show fairly consistent wintering distributions and migratory patterns regardless of climatic year type.
LeConte’s sparrows expand their wintering range in La Nina years, and concentrate their wintering range in El Nino years. Additionally, they migrate north earlier in La Nina years.